CHAPTER X 



" GROUSE DISEASE " CONTINUED STRONGYLOSIS l 



PART I. THE THREADWORMS (Nematoda) 2 

 By Dr A. E. Shipley 



PART II. ON THE DEVELOPMENT AND BIONOMICS OF T&ICHOSTRONGYLUS 



PERGRACILIS 



By Dr Robert T. Leiper 



(I.) Family Strongylidae 



(i.) TRICHOSTRONGYLUS PERGRACILIS (Cobbold) 



Synonym : Strongylus gracilis Cobbold 



THIS round-worm was first described under the name of Strongylus pergradlis 

 (Cobbold), by Cobbold, 3 whose words we quote : 



" Characters.- Body filiform, finely striated, gradually diminishing 

 in front, uniform in thickness below ; head bluntly pointed, with a simple oral 

 aperture ; tail of the male furnished with a bilobed bursa, each half supporting four 

 pointed rays ; -spicules two, thick, and slightly divergent ; tail of the female 

 slightly swollen above the subterminal anal orifice, rather sharply pointed at the 



tip ; vaginal opening situated at the upper part of the inferior sixth of the 

 body. 



" Length of male ^ inch to f inch ; body T $ Tr inch in diameter, tapering 

 anteriorly to -j^nnr inch at the head ; greatest breadth immediately above the bursa 

 inch. 



1 The term " Strongylosis " is employed in this chapter to denote the disease caused by Tricho- 

 strongylus peryracilis (Cobbold) ; though it would perhaps be more strictly correct to name the disease 

 Trichostrongy losit. 



2 Reprinted with slight alterations from the Proceedings of the Zoological Society of London, 1909. 



3 Cobbold " Grouse Disease," p. 16. 



207 



